1. Field of the Invention
This invention relates to wireless modems and, more particularly, software definable radio frequency (RF) wireless modems.
2. Description of Related Art
RF wireless modems are currently used in many portable devices, such as laptops, Personal Digital Assistants (PDAs), etc. Generally, these wireless modems are designed to transmit and receive data via a specific air interface. An air interface includes both a designated frequency band and a protocol for communication. Conventional wireless modems take advantage of this air-interface-specific design by implementing logic particular to the air interface, such as logic for protocol handling, in hardware. This creates faster and lower power modems, but at the cost of requiring the functionality of the modem to be fixed upon leaving the factory.
This drawback of conventional wireless modem design has been recognized in the industry, and many companies and standards groups are currently attempting to design software definable wireless modems. A software definable wireless modem would be capable of transmitting and receiving data over multiple air interfaces by reconfiguring its hardware as needed. In theory, software for a particular new air interface could be received by the device, such as by downloading it over a current air interface, allowing a user of the device to switch air interfaces as desired.
This potential flexibility in wireless modem communication would create a number of advantages. For example, the same portable device could be used when travelling to another part of the world, where an alternate air interface is preferable, without having to reserve space in memory for the software designed for the alternate air interface when not travelling. Additionally, alternate air interfaces could be used by the same device within the same locale at different times, depending on factors such as current cost of using a specific network and data rate needed for a particular task. However, in practice, designing this flexibility into a wireless modem has proven difficult.
In particular, the difficulty arises because a software definable modem will utilize hardware that is capable of transmitting and receiving over multiple frequency bands and using multiple protocols. Thus, most of the speed and power consumption characteristics, as well as the storage space requirements for the software, of a software definable modem are created by the manner of implementation in software. As more flexibility and generality are built into the software, the storage space requirements increase and the speed and power consumption characteristics generally worsen.
For example, some have suggested the use of a CORBA (Common Object Request Broker Architecture) type architecture to support both infrastructure and handheld devices for any type of communication configuration, including wireless configurations. However, CORBA is very complex because it attempts to make the network completely transparent by allowing execution of any class available on the network as if it is located on the local machine; CORBA writes all the interfaces between different machines. This complexity makes CORBA software excessively large, power consumptive, and greedy for processor cycles.
Therefore, what is needed is a software design approach for software definable wireless modems that provides as much flexibility as possible, while minimizing memory requirements, processor time and power consumption.